Method of making a heat exchanger



June 15, 1965 c. BAILYS I 3,183,725

A METHOD OF MAKING A HEAT EXCHANGER Original Filed July 26, 1957 2Sheets-Sheet 1 June 15, 1965 c. BAILYS 3,188,725 METHOD OF MAKING A HEATEXCHANGER Original Filed July 26, 1957 2 Sheets-Sheet 2 fnuerzZ'bi-v Cal #3019:

United 3,188,725 METHOD OF MAKING A HEAT EXCHANGER Carl L. Bailys,Detroit, Mich., assignor to Borg-Warner This application is a divisionof an earlier filed case 1 Serial Number 674,516, filed July 26, 1957entitled Heat Exchanger, and now US. Patent 2,991,047.

This invention relates to heat exchangers and, more particularly, to aheat exchanger of the tube sheet type fabricated from a plurality ofsheets of metal selectively bonded each to the other at predeterminedzones to define intermediate unbonded zones which may be complementallyshaped, as by hydroforming and the like, to form spaced tubes forpassage of fluid.

This invention is primarily directed to a heat exchanger of the statedtype in which a portion of the web between the tubes remains unbonded,in which a plurality of fins are formed in the web and in which theseveral plies forming the fins are separated to form singlethicknesspanels so that the total heat exchange surface area is substantiallyincreased.

A primary object of the invention is, therefore, to provide a heatexchanger of the stated type having all of the advantages of themultiple-sheet construction, yet exhibiting a substantial increase inheat transfer area.

Another object of the invention is to provide a heat exchanger of themultiple-sheet type having a plurality of parallel integral tubesseparated by webs having a plurality of angularly extending integralfins in heat conductive relation thereto, in which the several pliesforming the fins are separated to reduce the effective thickness of thefins and to form passages therebetween for the flow of air to thatefficient heat transfer is afforded.

Another object of the invention is to provide a heat exchanger of thetype described, in which the fins are integral with the tubes, inintimate heat conducting relation thereto and are so formed to effectturbulence in the heat exchange fluid during the course of its passagetherethrough.

A further object of the invention is to provide a heat exchanger; of thestated type characterized by ease of manufacture, efficiency andfacility of use, convenience in form, and improved functionalcharacteristics.

A more particular object of the invention is to provide a heat exchangerof the tube sheet type in which a plurality of sheets of similar metalare integrally bonded at preselected zones, in which tubular passagesare formed in certain of said unbonded zones for the flow of heatexchange fluid, in which the sheets in others of said unbonded zones areslit or partially severed therefrom to form strips which are bent toassume an angular relation with respect to the plane of the sheets thusforming a plurality of openings for the fiow of heat exchange fluid andin which each strip is separated to form a plurality of single fins forsecondary heat exchange between the tubular passages and fluid flowingthrough the fins.

3,188,725 Patented June 15, 1965 the fin formation is effected in such amanner that torsional stresses are substantially reduced and in whichthe formation of single-thickness fins is. facilitated.

Other objects and features of the invention will be readily apparent tothose skilled in the art from the specification and appended drawingsillustrating certain preferred embodiments in which:

FIGURE 1 is a front elevational view of a heat exchanger made inaccordance with the present invention;

FIGURE 2 is an edge view showing a preform of the present heatexchanger, in an intermediate state of formation, in which parallelbonded zones of a multiplesheet unit are illustrated.

FIGURE 3 is a view similar to FIGURE 2, but showing a heat exchangerpreform in the next subsequent stage of development in which certain ofthe unbonded zones are formed into spaced parallel tubes for passage offluid;

FIGURE 4 is an enlarged fragmentary sectional plan view of a heatexchanger fin made in accordance with the present invention;

FIGURE 5 is a sectional plan view taken substantially on line 5-5 ofFIGURE 4; and

FIGURE 6 is an enlarged elevational sectional view taken substantiallyon line 6-6 of FIGURE 4.

Referring now to the drawings and more particularly to FIGURE 1, theheat exchanger of the present inven-- tion is in the form of a tubesheet indicated generally by reference numeral 10 and in the illustratedembodiment includes a first sheet 6 of metal, such as aluminum or thelike, and a second sheet 8 of similar metal bondedto the sheet 8 atpredetermined zones to define headers consisting of an upper manifold 12and a lower manifold 14, and a fin unit or matrix 16 interposedtherebetween and having a plurality of integrally formed parallel tubes18 connecting the manifold 12 and the manifold 14 and spaced each fromthe other by webs 19.

The tubular passages 18 of the present heat exchanger I may beintegrally formed by the process of the Reynolds Metal Co. described inthe February 1956, issue of the magazine Modern Metals, or by similarprocesses, such as the Roll-Bond process. In the present disclosure theterm tube sheet has the same meaning as in those processes and refers toan integral combination of tubportions of the webs 19 joining adjacenttubes 18, are

slit along parallel lines to form contiguous strips. The strips of eachweb 19 are shaped, by bending or the like, to form a fin section 20having a plurality of multiply fins 22 spaced each from the other todefine openings 23 therebetween for free passage of cooling fluid, or

fiuid to be cooled, such as air or the like, in a directionsubstantially perpendicular to the plane of the web 19. It will be notedthat the unbonded fin matrix constitutes substantially all of theunbonded areas between the conduits to enhance heat transfer. In thepresent instance, the fins 22 are angularly disposed with respect to theplane of the web 19 and are desirably bent into the conamenable toseparation of the sheets 6 and 8 in the area heat transfer area is ofthe fins 22 so that the effective substantially increased.

' Referring now more particularly to FIGURES'4 and 5, each of the multiply fins 22 includes separate panels 24 spaced each from the other toform therebetween passage 26 substantially equal in width to theopenings 23. Each of the fin panels 24 may be considered asingle-thickness fin and includes-a pair of curved portions 28 extendingoutwardly in both directions from the plane of the web 19, and a centralportion 32 extending substantially perpendicular to the plane of the web19 and joining the portions 28. It will be noted that the several finpanels 24 diverge each from the other to form the passage 26. Theportions 32 are shown as beingparallel each to the other but it will bea-ppreciatedthat they may assume any relation. For instance, theportions 32 may be bowed.

ln forming the heat exchanger of the present invention, the sheets 6 and8 are provided with a suitable parting compound along parallel paths.Certain of these paths are for the formation of the passages 18 whilealternate paths are for the formation of the fins 22. The sheets arethen juxtaposed and subjected to a hot rolling .by way of limitation andthe scope of my invention is defined solely by the appended claims whichshould be construed as broadly as the prior art will permit.

I claim! 1. A method for making a heat exchanger of the tube sheettypecomprising the steps of integrally bonding two sheets'of metal each tothe other along parallel lines to form therebetween unbonded zones,expanding certain of said unbonded zones to form fluid passages,transversely slitting others of said unbonded zones between said fluidpassages to form a series of strips, bending said strips to form aseries of fins extending angularly to the plane of said sheets, suchthat each of said fins extend from both sides of the plane of saidsheets, and separating the plies of said fins to form a plurality ofmulti-ply fins.

2. A method of making a heat exchanger of' the tube sheet typecomprising the steps of integrally bonding two sheets of material eachto the other along parallellines to form therebetween tube and finunbonded zones, expanding said tube unbonded zones hydraulically to formfluid passages, transversely slitting said fin unbonded zones tooperation to join the sheets in-the zones between the paths of partingcompound. The passages 18 are then hydraulically formed intheconventional manner so that the blank assumes the configuration shown inFIGURE 3.

The blank is then provided with a plurality of spaced parallel slitsbetween each pair of tubes ,18. The'strips between each pair of slitsare then bent to form the multiply fins 22. Then the fins'22 are splitby means of a wedge, drift, or other suitable means to form the separatepanels or single-thickness fins 24. It is contemplated that the panels24 of the several fins 22 may be conveniently separated simultaneously.

It will be apparent from; the foregoing description that when thepresent device is used, for example, as 'a heat exchanger for an airconditioning systemithat fluid to be cooled or liquified may passintothe upper manifold 12 and thence downwardly through the severaltubes 18 to the manifold 14. During the course of 'its passage, thefluid is subject to heat exchange with air flowing through: the openingsbetween the several multi-ply fins 22 and through the passages 26defined by the several singlethickness panels forming a part of each fin22. It will be appreciatedthat the air may be at a temperature level.

higher or lower than the temperature level of the fluid. The air flowsinto contact with the several tubes 18 to effect primary heat exchange,while secondary heat exchange is afforded by contact of the air with theseveral panels 24 of the fins 22. In the present construction free flowof heat between the tubes 18 and the fins 22 is made possible by thefact that the portions of the intervening. webs are integrally bonded,there being no solder or brazing therebetween to hinder this flow ofheat. The gradual curvature .of the distorted portions28 assumes freedomfrom torsional stress in these areas.

The heat exchanger of the present invention exhibits importantadvantages over prior constructions in that the conduction of heat fromthe walls defining the passages 18 to the fins 22 is facilitated, sinceboth sides of the fin panels 24 are exposed to the flow of air. Sincethe thickness of each section is only a fraction of the thickness of thecomposite blank, the passage of heat from the fin panels is enhanced.The present heat exchanger is a' unitary structure which may beconveniently formed- According to the present method, the passages 18may be formed after the slitting step, if desired.

While'I'have described my invention in connection with certain specificembodiments thereof, it is to be understood that this is by way ofillustration and not form a series of contiguous parallel strips,bending said strips to form angularly extending fins and to formopenings encompassing the major area of said fin unbonded zonetherebetween, and separating the sheets of said fins to formseparatesingle-thickness multi-ply fins.

3. A method of making a heat exchanger of the sheettube type wherein twoplies of heat conductive sheet material are bonded together at certainareas, comprising the following steps: 'sandwiching strips of separationmaterial between said two plies of heat conductive sheet material todefine spaced apart fluid 'header patterns and a plurality of spacedapart conduit patterns and to define web patterns in a zone intermediatesaid spaced apart conduit patterns and separated from said conduitpatterns and separated from said header patterns and bonding said pliestogether at zones not protected by the separation material to accomplishthereat total integration of one ply to the other ply and forming asheet-tube means; expanding certain of said unbonded zoneshydraulically" to form fluid head rs interconnected by a system ofconduits and having sa conduits each separated by webbing comprisingsaid two plies. in contiguous unexpanded and unbonded relation;providing slits in said web,- bings extending laterally through both ofthe plies and extending along'the plane of the webbing substantiallybetween the bonded zones circumscribing each said webbing, said slitsbeing provided in a pattern to form generally elongate panels eachhaving opposite ends integrally connected to the sheet-tube means;turning said panels with the said two plies in contiguous relation fromthe plane of .the webbing about a longitudinal axis of the panels in adirection transverse to the plane of the webbing to permit heat exchangefluid to pass through the plane of the webbing; and separating thecontiguous plies ,of said turned panels to form regularly laterallyspaced heat exchanger fins which maximize the efficiency of the device.

4. A method of making a heat exchanger of the sheet- 7 tube type whereintwo plies of heat conductive sheet material arej'bonded together atcertain areas, comprising the following steps: sandwiching strips ofseparation material between said two plies of heat conductive sheetmaterial to definespaced apart conduit patterns and to define webpatterns in a zone intermediate saidspaced apart conduit patterns andseparated from said spaced apart conduit patterns and bonding said pliestogether webbing substantially between the bonded zones circumscribingeach said webbing to form a plurality of double ply panels; turning saidpanels with said two plies in contiguous relation from the plane of thewebbing in a direction transverse to the plane of the webbing to permit5 heat exchange fluid to pass through said webbing plane; and laterallyseparating the contiguous plies of said turned panels to form regularlyspaced heat exchanger fins which maximize the efficiency of the device.

6 References Cited by the Examiner UNITED STATES PATENTS 2,759,247 8/56Grenell et a1 29-1573 2,856,164 10/58 Adams 2 9l57.3 2,999,308 9/61Pauls 29--157.3

WHITMORE A. WILTZ, Primary Examiner.

HYLAND BIZOT, Examiner.

1. A METHOD FOR MAKING A HEAT EXCHANGER OF THE TUBE SHEET TYPECOMPRISING THE STEPS OF INTEGRALLY BONDING TWO SHEETS OF METAL EACH TOTHE OTHER ALONG PARALLEL LINES TO FORM THEREBETWEEN UNBONDED ZONES,EXPANDING CRETAIN OF SAID UNBONDED ZONES TO FORM FLUID PASSAGES,TRANSVERSELY SLITTING OTHERS OF SAID UNBONDED ZONES BETWEEN SAID FLUIDPASSAGES TO FORM A SERIES OF STRIPS, BENDING SAID STRIPS TO FORM ASERIES OF FINS EXTENDING ANGULARLY TO THE PLANE OF SAID SHEETS, SUCHTHAT EACH OF SAID FINS EXTEND FROM BOTH SIDES OF THE PLANE OF SAIDSHEETS, AND SEPARATING THE PLIES OF SAID FINS TO FORM A PLURALITY OFMULTI-PLY FINS.